I've written a unit test which seems to demonstrate that the Repeatable Read semantics are not being followed for PojoCache under 1.4.0.BETA2. Even though the test uses DummyTransactionManager, I understand that the locking semantics should still be correct.

In summary, I create two threads, each with their own PojoCache instance, but in the same cluster. The 1st thread reads a value from the cache within a transaction, the 2nd thread then writes a new value under that FQN, and the 1st thread then re-reads the value (within the original transaction), and gets a non-repeatable read, i.e. the value as written by thread 2.

When I read the source code for PojoCache, I see that explicit locks are acquired for a putObject() or removeObject(), but not for getObject().

Is this a flaw, or am I mis-understanding the applicability of isolation level within this context? It doesn't seem to follow ACID semantics.

Anyway, here's the test case, plus the cache config file:

package test;

import java.io.InputStream;
import java.util.concurrent.Callable;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

import junit.framework.TestCase;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.jboss.cache.PropertyConfigurator;
import org.jboss.cache.aop.PojoCache;

public class RepeatableReadTest extends TestCase {

 private final CountDownLatch startSignal = new CountDownLatch(1);
 private final CountDownLatch doneSignal = new CountDownLatch(2);

 private final CountDownLatch signalA = new CountDownLatch(1);
 private final CountDownLatch signalB = new CountDownLatch(1);

 private final ExecutorService executor = Executors.newCachedThreadPool();

 @Override
 protected void tearDown() throws Exception {
 executor.shutdownNow();
 }

 public void test() throws Exception {
 Log log = LogFactory.getLog(getClass());

 log.info("Creating and starting worker threads");
 executor.submit(new Worker1());
 executor.submit(new Worker2());

 log.info("Seeding cache with initial value for /test");
 PojoCache cache = createCache();
 cache.putObject("/test", "value1");

 startSignal.countDown();
 doneSignal.await();
 }

 class Worker1 implements Callable {
 private final PojoCache cache = createCache();
 private Log log = LogFactory.getLog(getClass());

 public Object call() throws Exception {
 startSignal.await();

 log.info("Beginning new tx and reading value");
 cache.getTransactionManager().begin();
 log.info("Cache contains value for /test : " + cache.getObject("/test"));

 log.info("Sending signal to thread 2");
 signalA.countDown();

 log.info("Waiting for signal from thread 2");
 signalB.await();

 log.info("Cache contains value for /test : " + cache.getObject("/test"));

 log.info("Done");
 doneSignal.countDown();

 return null;
 }
 }

 class Worker2 implements Callable {
 private final PojoCache cache = createCache();
 private Log log = LogFactory.getLog(getClass());

 public Object call() throws Exception {
 startSignal.await();

 log.info("Waiting for signal from thread 1");
 signalA.await();

 log.info("Starting new tx and writing new value for /test");
 cache.getTransactionManager().begin();
 cache.putObject("/test", "value2");

 log.info("Committing");
 cache.getTransactionManager().commit();

 log.info("Sending signal to thread 1");
 signalB.countDown();

 log.info("Done");
 doneSignal.countDown();

 return null;
 }
 }

 private PojoCache createCache() throws RuntimeException {
 try {
 PojoCache cache = new PojoCache();
 InputStream configStream = getClass().getResourceAsStream("cache-service.xml");
 new PropertyConfigurator().configure(cache, configStream);

 cache.setClusterName(getName());

 cache.start();
 return cache;
 } catch (Exception ex) {
 throw new RuntimeException(ex);
 }
 }
}

<?xml version="1.0" encoding="UTF-8"?>

<!-- ===================================================================== -->
<!-- -->
<!-- Sample TreeCache Service Configuration -->
<!-- -->
<!-- ===================================================================== -->

<server>

 <!-- ==================================================================== -->
 <!-- Defines TreeCache configuration -->
 <!-- ==================================================================== -->

 <mbean code="org.jboss.cache.aop.PojoCache"
 name="test:service=PojoCache">

 <depends>jboss:service=Naming</depends>
 <depends>jboss:service=TransactionManager</depends>

 <!--
 Configure the TransactionManager
 -->
 <attribute name="TransactionManagerLookupClass">org.jboss.cache.GenericTransactionManagerLookup</attribute>

 <!--
 Isolation level : SERIALIZABLE
 REPEATABLE_READ (default)
 READ_COMMITTED
 READ_UNCOMMITTED
 NONE
 -->
 <attribute name="IsolationLevel">REPEATABLE_READ</attribute>

 <!--
 Valid modes are LOCAL
 REPL_ASYNC
 REPL_SYNC
 INVALIDATION_ASYNC
 INVALIDATION_SYNC
 -->
 <attribute name="CacheMode">REPL_SYNC</attribute>

 <!--
 Just used for async repl: use a replication queue
 -->
 <attribute name="UseReplQueue">false</attribute>

 <!--
 Replication interval for replication queue (in ms)
 -->
 <attribute name="ReplQueueInterval">0</attribute>

 <!--
 Max number of elements which trigger replication
 -->
 <attribute name="ReplQueueMaxElements">0</attribute>

 <!-- Name of cluster. Needs to be the same for all clusters, in order
 to find each other
 -->
 <attribute name="ClusterName">TestCache</attribute>

 <!-- JGroups protocol stack properties. Can also be a URL,
 e.g. file:/home/bela/default.xml
 <attribute name="ClusterProperties"></attribute>
 -->

 <attribute name="ClusterConfig">
 <config>
 <!-- UDP: if you have a multihomed machine,
 set the bind_addr attribute to the appropriate NIC IP address, e.g bind_addr="192.168.0.2"
 -->
 <!-- UDP: On Windows machines, because of the media sense feature
 being broken with multicast (even after disabling media sense)
 set the loopback attribute to true -->
 <UDP mcast_addr="228.1.2.3" mcast_port="48866"
 ip_ttl="64" ip_mcast="true"
 mcast_send_buf_size="150000" mcast_recv_buf_size="80000"
 ucast_send_buf_size="150000" ucast_recv_buf_size="80000"
 loopback="false"/>
 <PING timeout="2000" num_initial_members="3"
 up_thread="false" down_thread="false"/>
 <MERGE2 min_interval="10000" max_interval="20000"/>
 <!-- <FD shun="true" up_thread="true" down_thread="true" />-->
 <FD_SOCK/>
 <VERIFY_SUSPECT timeout="1500"
 up_thread="false" down_thread="false"/>
 <pbcast.NAKACK gc_lag="50" retransmit_timeout="600,1200,2400,4800"
 max_xmit_size="8192" up_thread="false" down_thread="false"/>
 <UNICAST timeout="600,1200,2400" window_size="100" min_threshold="10"
 down_thread="false"/>
 <pbcast.STABLE desired_avg_gossip="20000"
 up_thread="false" down_thread="false"/>
 <FRAG frag_size="8192"
 down_thread="false" up_thread="false"/>
 <pbcast.GMS join_timeout="5000" join_retry_timeout="2000"
 shun="true" print_local_addr="true"/>
 <pbcast.STATE_TRANSFER up_thread="true" down_thread="true"/>
 </config>
 </attribute>


 <!--
 Whether or not to fetch state on joining a cluster
 NOTE this used to be called FetchStateOnStartup and has been renamed to be more descriptive.
 -->
 <attribute name="FetchInMemoryState">true</attribute>

 <!--
 The max amount of time (in milliseconds) we wait until the
 initial state (ie. the contents of the cache) are retrieved from
 existing members in a clustered environment
 -->
 <attribute name="InitialStateRetrievalTimeout">15000</attribute>

 <!--
 Number of milliseconds to wait until all responses for a
 synchronous call have been received.
 -->
 <attribute name="SyncReplTimeout">15000</attribute>

 <!-- Max number of milliseconds to wait for a lock acquisition -->
 <attribute name="LockAcquisitionTimeout">10000</attribute>

 <!-- Name of the eviction policy class. -->
 <attribute name="EvictionPolicyClass"></attribute>

 <!--
 Indicate whether to use region based marshalling or not. Set this to true if you are running under a scoped
 class loader, e.g., inside an application server. Default is "false".
 -->
 <attribute name="UseRegionBasedMarshalling">true</attribute>
 </mbean>
</server>